Salt of (S)-pantoprazole and its hydrates

ABSTRACT

The invention relates to (−)-pantoprazole magnesium and its hydrates and to medicaments comprising these compounds.

SUBJECT-MATTER OF THE INVENTION

The present invention relates to novel salts of the active compound(S)-pantoprazole. The novel salts can be used in the pharmaceuticalindustry for preparing medicaments.

BACKGROUND OF THE INVENTION

Owing to their H⁺/K⁺-ATPase-inhibitory action,pyridin-2-ylmethylsulphinyl-1H-benzimidazoles, such as those known, forexample, from EP-A-0005129, EP-A-0166287, EP-A-0174726 and EP-A-0268956are of considerable importance in the therapy of disorders associatedwith an increased secretion of gastric acid.

Examples of active compounds from this group which are commerciallyavailable or in clinical development are5-methoxy-2-[(4-methoxy-3,5-dimethyl-2-pyridinyl)methylsulphinyl]-1H-benzimidazole(INN: omeprazole),(S)-5-methoxy-2-[(4-methoxy-3,5-dimethyl-2-pyridinyl)methylsulphinyl]-1H-benzimidazole(INN: esomeprazole),5-difluoromethoxy-2-[(3,4-dimethoxy-2-pyridinyl)methylsulphinyl]-1H-benzimidazole(INN: pantoprazole),2-[3-methyl-4-(2,2,2-trifluoroethoxy)-2-pyridinyl)methylsulphinyl]-1H-benzimidazole(INN: lansoprazole),2-{[4-(3-methoxypropoxy)-3-methylpyridin-2-yl]methylsulphinyl}-1H-benzimidazole(INN: rabeprazole) and5-methoxy-2-((4-methoxy-3,5-dimethyl-2-pyridylmethyl)sulphinyl)-1H-imidazo[4,5-b]pyridine(INN: tenatoprazole).

The above mentioned sulphinyl derivatives which, owing to theirmechanism of action, are also referred to as proton pump inhibitors or,abbreviated, as PPI, are chiral compounds.

DESCRIPTION OF THE RELATED ART

For the first time, the international patent application WO92/08716describes a chemical process, which allowspyridin-2-ylmethylsulphinyl-1H-benzimidazoles to be separated into theiroptical antipodes. The compounds mentioned as being prepared in anexemplary manner include, inter alia, the compounds (+)- and(−)-5-difluoromethoxy-2-[(3,4-dimethoxy-2-pyridinyl)methylsulphinyl]-1H-benzimidazole[=(+)- and (−)-pantoprazole]. The international patent applicationWO92/08716 mentions that the optical antipodes of thepyridin-2-ylmethylsulphinyl-1H-benzimidazoles, i.e. the (+)- and(−)-enantiomers or the (R)- and (S)-enantiomers, are useful as activecompounds in medicaments for the treatment of gastrointestinaldisorders. For the mode of application and the dosage of the activecompounds, reference is made, inter alia, to the European patent 166287.

The international patent applications WO94/24867 and WO94/25028 claimthe use of the compounds (−)- and (+)-pantoprazole for treating gastricdisorders in humans. Each stereoisomer is said to have medicaladvantages compared to the respective other stereoisomer. Thedescriptions also mention a number of different possible salts of thestereoisomers, and particular preference is given to the sodium salt.

In international patent application WO94/27988, certain salts of (+)-and (−)-omeprazole and methods for their preparation are disclosed.

The international patent application WO97/41114 describes a certainprocess for preparing magnesium salts ofpyridin-2-ylmethylsulphinyl-1H-benzimidazoles. What is described in anexemplary manner is, inter alia, the preparation of the magnesium saltof racemic pantoprazole. According to the given analytical data, thesalt that is prepared is racemic pantoprazole magnesium in anhydrousform.

The international patent application WO00/10995 describes the dihydrateof the magnesium salt of racemic pantoprazole.

A common property of all of the abovementioned PPI is their sensitivityto acids (ultimately essential for effectiveness) which becomes apparentin their strong tendency to decompose in a neutral and in particular anacidic environment, giving rise to intensely coloured decompositionproducts. In the past, there has been no lack of considerable efforts,in spite of the sensitivity of the PPI to acids, to obtain stable andstorable oral dosage forms comprising these PPI. Such stable andstorable oral dosage forms (for example tablets or capsules) are nowobtainable. However, the preparation of these oral dosage forms isrelatively complicated, and with respect to the packaging too, certaincomplicated precautions have to be taken so that the dosage forms aresufficiently stable on storage even under extreme storage conditions(for example in tropical regions at high temperatures and highatmospheric humidity). Furthermore, in the past, there has been no lackof efforts to tailor the release of the PPI in the human body in thebest possible manner to the respective requirements.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a chart which represents an X-ray powder diffraction diagramof (−)-pantoprazole magnesium dihydrate.

FIG. 2 is a chart which represents the acid inhibition achieved byintravenous administration of various pantoprazole magnesium enantiomersfrom zero to 300 minutes.

FIG. 3 is a chart which represents the acid inhibition achieved byintravenous administration of various pantoprazole magnesium enantiomersfrom approximately 150 to 450 minutes.

DESCRIPTION OF THE INVENTION

It has now been found that the sodium salt of (−)- or (S)-pantoprazole,which is particularly preferred in the international patent applicationWO 94/24867, does not form a stable storage form. During variousattempts to obtain a stable oral dosage form for (−)-pantoprazole, ithas now been found that the magnesium salt, in particular in hydrateform, has highly surprising stability properties, making it aparticularly suitable candidate for use in solid or oral dosage forms.Compared to the sodium salt of (−)-pantoprazole, the magnesium salt hasconsiderably improved stability properties. Thus, for example,(−)-pantoprazole magnesium dihydrate is, at 70° C., completely stablefor one week and shows virtually no discolouration or decomposition,whereas over the same period of time and under identical conditions, thecolour of the hydrate of (−)-pantoprazole sodium changes to brown, withformation of considerable amounts of decomposition products.

Furthermore, the (−)-pantoprazole magnesium hydrate, which is thepreferred subject of the invention, is a non-hygroscopic salt having adefined water content of about 4.4%, which corresponds to that of thedihydrate, whereas (−)-pantoprazole sodium absorbs water depending ondrying conditions and atmospheric humidity, and, correspondingly, itswater content varies from 2 to 12%. This absorption of water isreversible, so that it is difficult to adjust an exact water content.Surprisingly, not only the (−)-pantoprazole sodium, but also the(−)-pantoprazole calcium shows these poor stability properties. Thewater content of (−)-pantoprazole calcium varies from 4-8% depending ondrying conditions and atmospheric humidity.

Compared to the racemic pantoprazole magnesium dihydrate, the(−)-pantoprazole magnesium dihydrate has, surprisingly, betterwettability. a considerably higher dissolution rate at pH 7-7.4 and, atpH 10, about tenfold better solubility.

Accordingly, the invention provides in a first aspect the magnesium saltof (−)-pantoprazole [=(S)-pantoprazole]. Preferably, the inventionprovides the magnesium salt (−)-pantoprazole [=(S)-pantoprazole]hydrates, i.e. the hydrates of the compound magnesium(−)-bis{[5-(difluoromethoxy)]-2-[(3,4-dimethoxy-2-pyridinyl)methylsulphinyl]-1H-benzimidazolide}.Here, particular emphasis is given to hydrates, which—after drying underreduced pressure at 50° C.—have a water content of from about 4.0 toabout 6.7%, in particular from about 4.0 to about 5.5%. Particularpreference is given to the hydrate form which has a water content offrom about 4.0 to about 5.0%, in particular from about 4.2 to about4.6%, which corresponds to a dihydrate.

(−)-Pantoprazole magnesium and its hydrates can be used for thetreatment and prevention of all disorders, which can be treated orprevented by using PPI. In particular, (−)-pantoprazole magnesium andits hydrates can be used for treating gastric disorders. In thiscontext, particular mention should be made of the relatively highstability of (−)-pantoprazole magnesium in the form of its dihydrate. Onstorage under atmospheric conditions, the sum of by-products in(−)-pantoprazole magnesium dihydrate remains virtually constant, whereasin the case of (−)-pantoprazole sodium, under identical conditions(storage at 60-70° C.) the purity (according to HPLC) decreases from99.5 to 96-97%. This relatively high storage stability makes(−)-pantoprazole magnesium dihydrate particularly suitable for use inmedicaments.

The hydrates of (−)-pantoprazole magnesium are prepared in a mannerknown per se by reacting (−)-pantoprazole with a magnesium base, forexample a magnesium alkoxide, or from a readily soluble (−)-pantoprazolesalt (for example (−)-pantoprazole sodium) using a magnesium salt inwater or in mixtures of water with polar organic solvents (for examplealcohols, preferably methanol, ethanol or isopropanol, or ketones,preferably acetone).

Magnesium salts suitable for use in the process are, for example,magnesium chloride, magnesium bromide, magnesium fluoride, magnesiumiodide, magnesium formate, magnesium acetate, magnesium propionate,magnesium gluconate or magnesium carbonate. It is also possible to reactmagnesium alkoxides (for example magnesium methoxide, magnesiumethoxide, magnesium (iso)propoxide, magnesium butoxide, magnesiumhexoxide or magnesium phenoxide) in an alkoholate medium with(−)-pantoprazole or (−)-pantoprazole sodium and to crystallise the(−)-pantoprazole magnesium hydrates by addition of water. Furthermore,it is possible to recrystallise the (−)-pantoprazole magnesium hydratesfrom, e.g., methanol/water mixtures.

For use in solid, in particular oral, pharmaceutical formulations, the(−)-pantoprazole magnesium hydrate according to the invention is milledin order to obtain crystals with a particle size distribution of 90%,preferably 99% below 100 μm.

According to the invention, “(−)-pantoprazole” is understood to include“(−)-pantoprazole, substantially free of the (+)-enantiomer”.

The examples below illustrate the invention in more detail, withoutlimiting it, m. p. denotes melting point, min. denotes minute(s), hdenotes hour(s).

EXAMPLES 1. Magnesium(−)-bis{[5-(difluoromethoxy)]-2-[(3,4-dimethoxy-2-pyridinyl)methylsulphinyl]-1H-benzimidazolide}Dihydrate

At 20-25° C., 20.2 g (52.7 mmol) of (−)-pantoprazole{(−)-[5-(difluoromethoxy)]-2-[(3,4-dimethoxy-2-pyridinyl)methylsulphinyl]-1H-benzimidazole}were suspended in 200 ml of purified water. A solution of (55.2 mmol)sodium hydroxide in 10 ml of water was added, and the mixture wasstirred at 20-30° C. for 30 min. With addition of a filter aid (1 gHyflo-Super-Cel), the turbid solution was filtered. 6.32 g (31.2 mmol)of magnesium dichloride hexahydrate in 150 ml of water were then addeddrop by drop with stirring over a period of 30 min. After a further 30min., the precipitated solid was filtered off with suction using asuction filter, stirred with water (2×50 ml) and again filtered off withsuction. Drying under reduced pressure at 50-60° C. gave, in a yield of17.36 g (80%), a hydrate of magnesium(−)-bis{[5-(difluoromethoxy)]-2-[(3,4-dimethoxy-2-pyridinyl)methylsulphinyl]-1H-benzimidazolide}having a water content of 4.5-4.7% as a colourless to beige powder (m.p.158-161° C. with decomposition).

Specific rotation: α_(D) ^(20°)=−114°(c=0.5, measured in methanol)

For recrystallisation, 1.88 g of the hydrate were, at 55° C. dissolvedin 6 ml of methanol, and 20 ml of water were added with stirring. Acolourless to beige solid crystallized out. This gave the title compoundof m. p. 160-163° C. (with decomposition) having a water content of4.3-4.4%.

Alternatively, the title compound can also be prepared fromorganic-aqueous solvent mixtures. To this end, (−)-pantoprazole sodium,or (−)-pantoprazole together with one equivalent of aqueous, for example2N, sodium hydroxide solution, is dissolved in an organic solvent, forexample warm acetone. 0.5 to 0.55 equivalents of a magnesium salt (forexample magnesium chloride hexahydrate), dissolved in water, are addeddrop by drop, and the mixture is cooled with stirring. The precipitatedsolid is filtered off, washed with the solvent mixture in question anddried at 50° C. under reduced pressure until the weight remainsconstant. This gives the title compound as a colourless to beige powder.

2. Magnesium(−)-bis{[5-(difluoromethoxy)]-2-[(3,4-dimethoxy-2-pyridinyl)methylsulphinyl]-1H-benzimidazolide}Dihydrate

A. (−)-Pantoprazole-Na

36 g of (−)-pantoprazole were suspended in 180 ml of methyl isobutylketone (MIBK) and 18 ml of 2-propanol and heated to an internaltemperature of 45° C. The suspension was stirred at this temperature for15 min. At 50° C., 11 g of 30% (w/w) aqueous sodium hydroxide solutionwere slowly added drop by drop to this suspension. A clear to slightlyturbid solution resulted. This solution was stirred for a bit longer andthen filtered to give a clear solution.

The clear filtrate was slowly cooled to room temperature. Between 45° C.and 30° C. crystallization, which could be accelerated by seeding with(−)-pantoprazole sodium, began. The resulting suspension was stirred atan internal temperature of <20° C. for another 2 h. The suspension wasthen filtered, and the crystals were washed with 40 ml of MIBK.

Drying was carried out in a vacuum drying cabinet at <50 mbar and 40-45°C. [It is also possible to dispense with drying and to use the moistproduct (having an MIBK content of 10-20%) directly for step B]. Thewhite-beige crystalline product obtained after drying was hygroscopic.The water content was from 2 to 12%. The absorption and release of waterwere reversible. Yield: 34 g=90% of theory (based on anhydrous product).Specific rotation: a_(D) ^(20°)=−95 (c=0.5, measured in methanol, sodiumsalt having a water content of 12%). m. p.: 145-165° C. (decomposition,sodium salt having a water content of 2%); 102-109° C. (decomposition,sodium salt having a water content of 12%).

B. (−)-Pantoprazole-Mg

30 g of (−)-pantoprazole sodium salt (calculated anhydrous substance)were suspended in 260 ml of water. The suspension was heated to 35-40°C. and stirred at 35-40° C. for another 10 min. This gave a clearsolution. The clear solution was cooled to 22-27° C. 14.3 g of magnesiumchloride hexahydrate were dissolved in 100 ml of water, and at roomtemperature and with stirring, the solution was slowly added dropwise tothe (−)-pantoprazole sodium salt solution. The resulting suspension wasthen stirred at room temperature for another 4 h. The suspension was,under pressure, filtered through a Nutsche filter, and the product was,a little at a time, washed twice with 300 ml of water. Drying in avacuum drying cabinet at <50 mbar and 40-45° C. gave 27.5 g (90%) of thetitle compound of m. p. 160-163° C. Water content 4.3-4.4%; specificrotation: a_(D) ^(20°)=−129 (c=0.5, measured in methanol).

Recrystallisation of (−)-pantoprazole-Mg

For recrystallisation, 6.0 g of the (−)-pantoprazole-Mg-dihydrate were,at 55° C., dissolved in 18 ml of methanol. After 15 min, 90 ml of waterwere added with stirring to the orange-brown-solution. A colourless tobeige solid crystallised out. The resulting suspension was then stirredat 20-25° C. for another 1 hour. The solid was filtered off, washed with10 ml of water and dried under vacuum for 20 hours at 50° C. The yieldfor the title compound was 88% (5.26 g) with the following data:

M.P.: 161-165° C. (with decomposition)

Specific rotation: a_(D) ^(20°)=−130 (c=0.5, measured in methanol)

XRD-Data: The X-ray powder diffraction patterns were measured on aPhilips PW 1800 diffractometer at ambient temperature in the range of3°≦2φ≦80°. The X-ray powder diffraction patterns of (−)-pantoprazolemagnesium dihydrate, are characterized by reflections with strong (2φabout 23°), medium (2φ about 6°, 12°, 14°, 17°, 19°, 22°, 24°, 25°, 30°,33° and 35°) and small (2φ about 13°, 16°, 26°, 28°, 33° and in therange of 36° to 62°) intensities. An exemplary X-ray powder diffractiondiagram is shown in FIG. 1.

Commercial utility

(−)-Pantoprazole magnesium and its hydrates have useful pharmacologicalproperties, rendering them commercially utilizable. In particular, theyhave a pronounced inhibitory effect on the secretion of gastric acid andexcellent gastrointestinal protective action in warm-blooded animals, inparticular man. Here, the compounds according to the invention aredistinguished by a highly selective action, an advantageous duration ofaction, a particularly high bioavailability, a metabolization profilethat is uniform among different individuals, the lack of significantside-effects and a wide therapeutic spectrum.

In this context, “gastrointestinal protection” is to be understood asthe prevention and treatment of gastrointestinal disorders, inparticular gastrointestinal inflammatory disorders and lesions (such as,for example, Ulcus ventriculi, Ulcus duodeni, gastritis, irritable bowelowing to an increased production of acid or as a result of medicaments,GERD, Crohn's disease, IBD) which may be caused, for example, bymicroorganisms (for example Helicobacter pylori), bacterial toxins,medicaments (for example certain antiphlogistics and antirheumaticdrugs), chemicals (for example ethanol), gastric acid or stress.

With their excellent properties. (−)-pantoprazole magnesium and hydratesthereof are, in various models for the determination of antiulcerogenicand antisecretory properties, surprisingly clearly superior to the priorart compounds, in particular with respect to their stability and theirmetabolization properties. Owing to these properties, (−)-pantoprazolemagnesium and hydrates thereof are highly suitable fur use in human andveterinary medicine, where they are used, in particular, for thetreatment and/or prophylaxis of gastrointestinal disorders.

Accordingly. the invention furthermore provides the use of(−)-pantoprazole magnesium and hydrates thereof for the treatment and/orprophylaxis of the abovementioned diseases.

The invention also embraces the use of (−)-pantoprazole magnesium andhydrates thereof for preparing medicaments used for the treatment and/orprophylaxis of the abovementioned diseases.

The invention also provides medicaments comprising (−)-pantoprazolemagnesium and hydrates thereof.

The medicaments are prepared by processes known per se which arefamiliar to the person skilled in the art. As medicaments,(−)-pantoprazole magnesium hydrates are employed either as such or,preferably, in combination with suitable pharmaceutical auxiliaries orcarriers in the form of tablets, coated tablets, capsules,suppositories, plasters (for example as TTS), emulsions, suspensions orsolutions, where the content of active compound is advantageously fromabout 0.1 to about 95% and where it is possible to producepharmaceutical dosage forms (for example flow-release forms or entericforms) which, by the appropriate choice of auxiliaries and carriers, aretailored for the active compound and/or the desired onset of actionand/or the duration of action.

The auxiliaries or carriers suitable for the desired pharmaceuticalformulations are known to the person skilled in the art. In addition tosolvents, gel formers, suppository bases, tabletting auxiliaries andother carriers for active compounds, it is possible to use, for example,antioxidants, dispersants, emulsifiers, antifoams, flavour-maskingagents, preservatives, solubilizers, colorants or, in particular,permeation promoters and complex formers (for example cyclodextrins).

(−)-Pantoprazole magnesium and hydrates thereof can be administeredorally, parenterally or percutaneously.

In human medicine, it has generally been found to be advantageous toadminister (−)-pantoprazole magnesium hydrates, when given orally, in adaily dose of from about 0.1 to about 2, preferably about 0.2 to about1.5 and in particular about 0.3 to about 1.1, mg/kg of body weight[based on (−)-pantoprazole], if appropriate in the form of a pluralityof, preferably 1 to 4, individual doses, to obtain the desired result.For parenteral treatment, it is possible to use similar or (inparticular when the active compounds are administered intravenously)generally lower dosages. The optimum dosage and the type ofadministration of the active compounds required in each case can easilybe determined by the person skilled in the art.

A further aspect of the invention is thus a medicament, comprising a(−)-pantoprazole magnesium hydrate together with customary auxiliaries,where the single dose comprises from about 10 to about 100 mg of(−)-pantoprazole.

A further aspect of the invention is a medicament, comprising a(−)-pantoprazole magnesium hydrate together with customary auxiliaries,where the single dose comprises from about 20 to about 80 mg of(−)-pantoprazole.

A further aspect of the invention is the use of (−)-pantoprazolemagnesium and hydrates thereof for treating gastrointestinal disorders.

A further aspect of the invention is the use of (−)-pantoprazolemagnesium and hydrates thereof for treating gastrointestinal disordersin patients who are slow metabolizers.

A further aspect of the invention is the use of (−)-pantoprazolemagnesium and hydrates thereof for treating gastrointestinal disordersin patients who have a risk of drug interactions.

A further aspect of the invention is the use of (−)-pantoprazolemagnesium and hydrates thereof for treating gastrointestinal disordersin patients who need an inhibition of acid secretion for an extendedperiod of time.

A further aspect of the invention is a medicament for treatinggastrointestinal disorders for use in patients who are slowmetabolizers, comprising a (−)-pantoprazole magnesium hydrate togetherwith customary auxiliaries, where the single dose comprises from about10 to about 100 mg of(−)-pantoprazole.

A further aspect of the invention is a medicament for treatinggastrointestinal disorders for use in patients who are slowmetabolizers, comprising a (−)-pantoprazole magnesium hydrate togetherwith customary auxiliaries, where the single dose comprises from about20 to about 80 mg of (−)-pantoprazole.

A further aspect of the invention is a medicament for treatinggastrointestinal disorders for use in patients who have a risk of druginteractions, comprising a (−)-pantoprazole magnesium hydrate togetherwith customary auxiliaries, where the single dose comprises from about10 to about 100 mg of (−)-pantoprazole.

A further aspect of the invention is a medicament for treatinggastrointestinal disorders for use in patients who have a risk of druginteractions, comprising a (−)-pantoprazole magnesium hydrate togetherwith customary auxiliaries, where the single dose comprises from about20 to about 80 mg of (−)-pantoprazole.

A further aspect of the invention is a medicament for treatinggastrointestinal disorders for use in patients who need an inhibition ofacid secretion for an extended period of time, comprising a(−)-pantoprazole magnesium hydrate together with customary auxiliaries,where the single dose comprises from about 10 to about 100 mg of(−)-pantoprazole.

A further aspect of the invention is a medicament for treatinggastrointestinal disorders for use in patients who need an inhibition ofacid secretion for an extended period of time, comprising a(−)-pantoprazole magnesium hydrate together with customary auxiliaries,where the single dose comprises from about 20 to about 80 mg of(−)-pantoprazole.

If (−)-pantoprazole magnesium and hydrates thereof are to be used fortreating the abovementioned diseases, the pharmaceutical preparationsmay also comprise one or more pharmacologically active ingredients fromother groups of medicaments. Examples that may be mentioned includetranquilizers (for example from the group of the benzodiazepines, e. g.,diazepam), spasmolytic drugs (e. g., bietamiverine or camylofine),anticholinergic drugs (e. g., oxyphencyclimine or phencarbamide), localanesthetics (e. g., tetracaine or procaine), and optionally alsoenzymes, vitamins or amino acids.

In this context, particular emphasis is given to the combination of thecompounds according to the invention with other pharmaceuticals whichbuffer or neutralize gastric acid or which inhibit the secretion ofacid, such as, for example, antacids (such as, for example, magaldrate)or H₂ blockers (e. g., cimetidine, ranitidine), and with gastrinantagonists with the aim to enhance the main action in an additive orsuperadditive-sense and/or to eliminate or reduce side-effects or toobtain a more rapid onset of action. Mention may also be made of thefixed or free combination with NSAIDs (such as, for example,etofenamate, diclofenac, indometacin, ibuprofen or piroxicam) forpreventing the gastrointestinal damage caused by the NSAIDs, or withcompounds, which modify gastrointestinal motility, or with compounds,which reduce the incidence of transient lower esophageal sphincterrelaxation (TLOSR), or with antibacterial substances (such as, forexample, cephalosporins, tetracyclins, penicillins, macrolides,nitroimidazoles or else bismuth salt) for controlling Helicobacterpylori. Antibacterial combination partners that may be mentionedinclude, for example, mezlocillin, ampicillin, amoxicillin. cefalothin,cefoxitin, cefotaxim, imipenem, gentamycin, amicacin, erythromycin,ciprofloxacin, metronidazole, clarithromycin, azithromycin andcombinations thereof (e. g., clarithromycin+metronidazole oramoxicillin+clarithromycin).

Pharmacological Investigations 1. Metabolization on Human LiverMicrosomes

I. Materials and methods

I) Human liver microsomes: Pantoprazole racemate and the (+)- and(−)-enantiomers (10 μM each) were incubated with human liver microsomes(source: TEBU, incubation in 1 mg/ml protein, 100 mM Tris-HCl, pH 7.4, 1mM NADPH₂). Reaction was terminated after 30 and 120 minutes by liquidnitrogen, the parent compound was detected by HPLC (10 mM KH₂PO₄, pH7.4, acetonitril gradient 20-48%).

II) Recombinant CYP 2C19 (source: GENTEST); incubation method asdescribed under I) (in presence of 0.1 mg/ml protein).

III) Recombinant CYP 3A4 (source: GENTEST); incubation method asdescribed under I) (in presence of 0.3 mg/ml protein).

II. Results

(−)-Pantoprazole (26%, mean, n=3, SD=3, 120 min) was significantly lessmetabolized on human microsomes compared to the (+) enantiomer (44%,mean n=3, SD=2, 120 min) and the racemate (44%. mean, SD=4, 120 min),respectively. Similarly, on CYP2C19 the values were for:(−)-pantoprazole (54%, mean, n=3, SD=3, 120 min); (+)-pantorazole: (64,mean, n=3, SD=5, 120 min); racemate (67%, mean, n=3, SD=1, 120 min). Thebiotransformation on CYP3A4 was not different among the enantiomers andthe racemate.

The lower biotransformation rate of (−)-pantoprazole compared to the (+)enantiomer lets expect a lower biotransformation in vivo as well withthe result of higher plasma levels of (−)-pantoprazole. Clinically, thismay translate into an even lower risk for drug interactions for(−)-pantoprazole.

2. Inhibition of Acid Output in the Ghosh-Schild Rat After I.V.Administration

I. Introduction

Pyridin-2-ylmethylsulphinyl-1H-benzimidazoles are chiral compounds. Thetwo enantiomers, which exist for eachpyridin-2-ylmethylsulphinyl-1H-benzimidazole, are prodrugs that requireacid-catalyzed activation into a sulfenamide, which is achiral and forboth enantiomers identical. The achiral sulfenamide then reactscovalently with cysteines of the gastric proton pump to block it. Hence,in pharmacodynamic terms, the two enantiomers should display identicalpotencies and efficacies, provided they are in vivo metabolized at thesame rate. This was assumed in case of pantoprazole based on rat datathat have shown almost identical percentage inhibitions by the twoenantiomers of the sodium salt (see Kromer, W., Scand. J. Gastroenterol.2001, 36, suppl. 234: 3-9, FIG. 5). Such previous experiments covered3.5 hours following intravenous drug administration and have now beenrepeated with the two enantiomers of the magnesium salt of pantoprazole.In addition, the effects of the two enantiomers of the magnesium salt ofpantoprazole have now been determined in the time interval between 3 and7.5 hours following i.v. administration of 1 μmol/kg of the magnesiumsalts of the two enantiomers.

II. Materials and methods.

Female Sprague Dawley CD rats (190-210 g body weight) were anaesthetisedwith 1.5 g/kg i.m. of urethane, in 5 ml/kg physiologic saline. Thetrachea was intubated and both, the left external jugular vein (for drugadministration) and left femoral vein (for pentagastrin infusion) werecannulated. An esophagus/cardia-cannula (diameter: 1.7 mm) was insertedtransorally, and a pylorus-cannula (diameter: 2.6 mm) was insertedthrough the duodenum, and both were secured with a ligature. The pyloriccatheter was led through the right abdominal wall. Body temperature wasmaintained at 37.0±0.2° C. by means of infrared radiation and electriccushion (automatic infinite control via rectal temperature probe). Afterthorough flushing (about 50-100 ml), the stomach was continuouslyperfused with 0.5 ml/min of physiologic saline (37° C.). In theeffluate, collected at 15 min intervals, the pH as well as the acidoutput were determined, the latter by titration to pH 7 with freshlyprepared 0.01 N NaOH.

Gastric secretion was stimulated by a continuous intravenous infusion(left femoral vein) of 1 μg/kg×min pentagastrin (in 1.6 ml/h physiologicsaline) starting after determination of two basal values of acidsecretion, i.e., 30 min after commencement of stomach perfusion. Seehorizontal bars in FIGS. 1 and 2 for pentagastrin-infusion. 1 μmol/kg of(−)-pantoprazole or (+)-pantoprazole-Mg was administered intravenouslyin a volume of 1 ml/kg body weight as an 30 sec i.v. injection. Controlsreceived the corresponding amount of physiologic saline. Note that 1μmol pantoprazole-Mg is equivalent to 2 μmol of the free acid ofpantoprazole.

Experiment 1: Drug administration 1 hour after commencement ofpentagastrin stimulation (see FIG. 2).

Experiment 2: Drug administration 3 hours prior to commencement ofpentagastrin stimulation (see FIG. 3).

III. Results

FIG. 2 of Experiment 1 clearly shows that the two enantiomers ofpantoprazole-Mg are equieffective in blocking acid output during thefirst 3.5 hours following drug administration 1 hour after commencementof pentagastrin stimulation.

In Experiment 2, where the drug was administered 3 hours prior tocommencement of acid stimulation by pentagastrin, and acid output wasmeasured over the following 4.5 hours, it was found, surprisingly, thatthe (−)-enantiomer was significantly superior to the (+)-enantiomer ininhibiting acid secretion (FIG. 3).

The (−)-enantiomer is significantly more effective than the(+)-enantiomer in the time interval between 3 and 7.5 hours after drugadministration. It is important to note that this difference in favourof the (−)-enantiomer is maintained and still significant even 7.5 hoursafter i.v. drug administration.

This unexpected finding could be explained for example, if thepreferential and favourable binding of pantoprazole to cysteine 822 ofthe proton pump was mainly due to the binding of its (−)enantiomer. Thiscould be therapeutically exploited by administering the (−)-enantiomerof pantoprazole in order to achieve a longer duration of action,compared to the racemate or to the other PPIs that do not bind tocysteine 822 at all (Shin, J. M., and Sachs. G., Gastroenterology 2002,123: 1588-1597).

1. (−)-Pantoprazole magnesium [(S)-pantoprazole magnesium] dihydrate,wherein (−)-pantoprazole magnesium is substantially free of the(+)-enantiomer.
 2. A (−)-pantoprazole magnesium dihydrate according toclaim 1, having a water content of from about 4.0 to about 5.0%.
 3. A(−)-pantoprazole magnesium dihydrate according to claim 1, having awater content of from about 4.2 to about 4.6%.
 4. A (−)-pantoprazolemagnesium dihydrate according to claim 1 with a particle sizedistribution of 99% below 100 μm.
 5. A (−)-pantoprazole magnesiumdihydrate according to claim 1 with X-ray powder diffraction patternswhich are characterized by reflections with strong (2φ about 23°),medium (2φ about 6°, 12°, 14°, 17°, 19°, 22°, 24°, 25°, 30°, 33° and35°) and small (2φ about 13°, 16°, 26°, 28°, 33° and in the range of 36°and 62°) intensities.
 6. A pharmaceutical composition comprising(−)-pantoprazole magnesium dihydrate, wherein (−)-pantoprazole magnesiumis substantially free of the (+)-enantiomer, together with a suitablepharmaceutical auxiliary or carrier.
 7. A pharmaceutical compositioncomprising (−)-pantoprazole magnesium dihydrate, wherein(−)-pantoprazole magnesium is substantially free of the (+)-enantiomer,together with a suitable pharmaceutical auxiliary or carrier, wherein(−)-pantoprazole is present in an amount from about 10 to about 100 mg.8. A method of treating a gastrointestinal disorder in a patientcomprising administering to a patient in need thereof a therapeuticallyeffective amount of (−)-pantoprazole magnesium dihydrate, wherein(−)-pantoprazole magnesium is substantially free of the (+)-enantiomerand wherein the patient needs an inhibition of acid secretion for anextended period of time.
 9. A (−)-pantoprazole magnesium dihydrateaccording to claim 2 with a particle size distribution of 99% below 100μm.
 10. A (−)-pantoprazole magnesium dihydrate according to claim 3 witha particle size distribution of 99% below 100 μm.
 11. A (−)-pantoprazolemagnesium dihydrate according to claim 2 with X-ray powder diffractionpatterns which are characterized by reflections with strong (2φ about23°), medium (2φ about 6°, 12°, 14°, 17°, 19°, 22°, 24°, 25°, 30°, 33°and 35°) and small (2φ about 13°, 16°, 26°, 28°, 33° and in the range of36° and 62°) intensities.
 12. A (−)-pantoprazole magnesium dihydrateaccording to claim 3 with X-ray powder diffraction patterns which arecharacterized by reflections with strong (2φ about 23°), medium (2φabout 6°, 12°, 14°, 17°, 19°, 22°, 24°, 25°, 30°, 33° and 35°) and small(20φ about 13°, 16°, 26°, 28°, 33° and in the range of 36° and 62°)intensities.
 13. A pharmaceutical composition comprising a(−)-pantoprazole magnesium dihydrate according to claim 2 together witha suitable pharmaceutical auxiliary or carrier.
 14. A pharmaceuticalcomposition comprising a (−)-pantoprazole magnesium dihydrate accordingto claim 2 together with a suitable pharmaceutical auxiliary or carrier,wherein (−)-pantoprazole is present in an amount from about 10 to about100 mg.
 15. A pharmaceutical composition comprising a (−)-pantoprazolemagnesium dihydrate according to claim 3 together with a suitablepharmaceutical auxiliary or carrier.
 16. A pharmaceutical compositioncomprising a (−)-pantoprazole magnesium dihydrate according to claim 3together with a suitable pharmaceutical auxiliary or carrier, wherein(−)-pantoprazole is present in an amount from about 10 to about 100 mg.17. A pharmaceutical composition comprising a (−)-pantoprazole magnesiumdihydrate according to claim 4 together with a suitable pharmaceuticalauxiliary or carrier.
 18. A pharmaceutical composition comprising a(−)-pantoprazole magnesium dihydrate according to claim 4 together witha suitable pharmaceutical auxiliary or carrier, wherein (−)-pantoprazoleis present in an amount from about 10 to about 100 mg.
 19. Apharmaceutical composition comprising a (−)-pantoprazole magnesiumdihydrate according to claim 5 together with a suitable pharmaceuticalauxiliary or carrier.
 20. A pharmaceutical composition comprising a(−)-pantoprazole magnesium dihydrate according to claim 5 together witha suitable pharmaceutical auxiliary or carrier, wherein (−)-pantoprazoleis present in an amount from about 10 to about 100 mg.